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A. Cotera (SETI Institute), A. Leistra (Steward Observatory)
Near-infrared imaging surveys such as the Two Micron All Sky Survey (2MASS) and the Deep NIR Southern Sky Survey (DENIS) provide a wealth of data, enabling searches for previously unknown stellar clusters. As part of a separate investigation into the Initial Mass Function (IMF) as a function of galactic environment, we have used published survey results, in addition to our own search of the 2MASS archive, to identify cluster candidates from a wide range of galactocentric radii.
On 14-15 July 2003, we obtained images of two of these cluster candidates, Object 11 (Dutra & Bica, 2000, A&A, 359, L9) and Object 41 (Dutra & Bica, 2001, A&A, 376, 434), at the 4 meter Anglo-Australian Telescope with the facility instrument IRIS2. IRIS2 utilizes a 1024X1024 HgCdTe array, with a pixel scale of 0.46", resulting in a 7.7'X7.7' field of view. When observed at this scale, the cluster candidates are revealed to be enhancements in stellar density due to a hole in the line of sight dust, and not actual clusters. The 2MASS search which identified these as cluster candidates used a 5'X5' FOV; when the 2MASS archive is examined with a 8'X8' FOV, a result similar to our higher resolution images is obtained. These results suggest that the 2MASS search criteria for stellar clusters in the galactic plane must chosen with extreme caution.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.